<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    let arr = [20,30,60,2,8,10,11,70];
    let sum = arr.filter(n=> n>=10).map(n=>n*0.5).reduce((s,n)=>s+n);
    console.log(sum);
</script>
</body>
</html>